I am looking for a way how to inform my user for example if I do some updates on the server that the application is not available on Friday from 2-3am. I was thinking maybe of a news feed or RSS. Is there a better way? Any ideas?

You could use states. In the creationComplete event for your application, check the time and set the state to a simple state with a Label stating server unavailable for maintenance if between the specified time, otherwise show the whole app state.